This invention relates to manually actuated foaming devices and more particularly, it concerns an improved foamer nozzle construction for use with collapsible bottles containing foamable liquid and air.
In my co-pending application Ser. No. 584,610 filed June 6, l975, now U.S. Pat. No. 3,985,271 there is disclosed a foam generating and dispensing device in which the discharge passageway of a cap adapted to be attached to a collapsible bottle containing foamable liquid and air is fitted with a porous element of rigid polymeric material having structural characteristics enabling direct support of a dip tube from the element as well as the formation in the element of a return air passageway and valve seat for a one-way ball check. The valve seat is spaced sufficiently from the end of the dip tube such that upon forcible collapse of the bottle to pressurize its contents, air or liquid, depending on the vertical orientation of the bottle, is caused to pass through the dip tube and outwardly into the porous element to be mixed with liquid (or air) passing directly through the element and discharged through the cap as foam. Upon relaxing the force collapsing the bottle, a negative pressure within the bottle is balanced with atmospheric pressure by return passage of air past the ball check, through the dip tube and to the bottle interior. A similar type of foam dispensing device is disclosed in U.S. Pat. No. 3,937,364 issued Feb. 10, 1976 to Herschel Earl Wright, through in this instance, the chamber and seat for the ball check valve is established by a tubular component separate from the porous element, itself.
Manually actuated foam dispensers of the type disclosed in the aforementioned references represent viable commercial candidates because of their effectiveness in achieving the desired intermixture of air and liquid at low pressures and also because of low manufacturing costs. In this latter respect, the foam generating components, namely, the porous block, dip tube and ball check, represent a three part subassembly which is capable of being press fit or otherwise secured directly in the interior large end of a standard tapered or frusto-conical nozzle on a premolded cap which, when secured to a collapsible bottle, provides the complete foam generating and dispensing unit.
A major problem with manually actuated foam dispensing devices, including those of the type aforementioned, is the attainment of a predictably uniform and preferably stiff consistency in the discharged foam while at the same time avoiding such resistance to fluid flow from the foamer as would require excessive application of force to collapse the bottle containing the foamable liquid and air. Consistency and foam stiffness turn largely on reducing to a minimum, bubble size in the foam, a factor in turn predicated on the size of passageways through which the liquid and air are passed for intermixing. Thus, it will be appreciated that optimizing the desirable characteristics in the foam is inconsistent with reduction of foam dispensing pressures. Optimum results with manual foaming devices are achieved, therefore, only by a careful correlation of the foamer components. In particular, the porous element through which the liquid and air are passed for mixing must be matched with the liquid used to produce the foam.
In addition, the development of a stiff foam, in which bubble size is minimized, enlarges the problems associated with the return of air to the bottle interior during each foaming cycle. In foamers of the aforementioned type, for example, that portion of the cap discharge nozzle extending beyond the porous block will be filled with foam at the time the bottle collasping force is released and the foam in the nozzle will resist the return of air through the ball check valve chamber in the porous block and dip tube to the interior of the bottle.